1. Field of the Invention
This invention is directed to an improvement of a speaker system, and more particularly to a speaker system which can be operative both as a twin-drive speaker system wherein two woofers are simultaneously driven and as a passive radiator.
2. Description of the Prior Art
There have conventionally been known the following compact speaker systems.
FIG. 1 shows a closed-type speaker system in which an enclosure containing a woofer W therein is completely closed from the outer air. Since the internal volume of the enclosure is small, the enclosure is configured in an acoustic suspension or in an air suspension.
FIG. 2 shows a bass-reflex speaker system in which a duct D is provided in the enclosure to utilize resonance of the duct D to improve reproduction of low-range sound.
FIG. 3 shows a passive radiator type speaker system in which a passive radiator P is driven by back pressure of a woofer to thereby increase low-range sound.
In the closed construction of FIG. 1, sound reproduction cannot be effected in low-range when the speaker system is a compact one with a small volume and a small diameter.
In this connection, the bass-reflex speaker system of FIG. 2, the passive radiator type speaker system of FIG. 3 or a system as shown in FIG. 4 which is of a closed type and includes two woofers are used. However if those constructions are used in speaker systems for cars, sound characteristic in low range varies depending on the shapes of cars and positions in a car room for mounting the speaker systems. For example, characteristic No. 2 obtained when the speaker system is positioned in a room without resonance and characteristic No. 1 obtained when the speaker system is mounted in a car room are different from each other as shown in FIG. 5. Although differences of the characteristic extremely vary depending on shapes of car bodies, it has been quite difficult, in the conventional speaker systems, to adjust the low-range sound characteristic for every car.